Pneumatics ensures food-processing reliability

Chicken is big business. The U.S. produced nearly 37 billion lb of commercial chicken in 2010, and the average American consumes more than 80 lb each year. Getting that much meat from farm to table relies heavily on advanced automation, where reliability is critical, and pneumatics often plays a central role.

For instance, an important step in preparing fresh chicken for the supermarket involves weighing, sizing, and sorting the fillets, wings, thighs, and drums from processed birds and packaging them quickly in a sanitary environment. The new Flexible Sizing & Packaging System for Poultry (FSPS-P) from Baader North America Corp., Kansas City, Kan., performs all these tasks, combining the functions of several individual machines into one all-encompassing system.

Conveyor belts on either side of the 60-ft long FSPS-P each handle about 180 pieces per minute, explains Doug Barnett, a senior design engineer with Baader. The chicken pieces travel across a moving conveyor scale, where they are weighed on the fly, then move on to one of eight stations along each conveyor, where they are automatically sorted per customer requirements and placed into various-size tray packs commonly found in grocery stores.

Beyond the tray-pack area, the remaining pieces on the two conveyors are discharged to the center of the FSPS-P, creating larger batches that are boxed for shipment, freezer storage, or future processing. Finally, conveyors carry the trays and boxes away.

Getting a handle on processing

Much of the sorting and handling is pneumatically powered. For instance, custom pneumatic rotary actuators — designed and built by Baader — drive paddles that shuttle products from the conveyors to the packing stations. The rack-and-pinion actuators are constructed of oil-impregnated nylon and stainless steel and are approved for food-handling applications.

Virtually all the remaining pneumatics on the machine, from actuators and valves to fittings and filters, are supplied by Festo Corp., Hauppauge, N.Y. For example, at the tray-pack stations, sorted batches drop into metal drawers. Festo’s DSNU air cylinders push the drawers out to operators, who pack the contents into trays, and retract them when the process is complete.

Twenty-six of the corrosion-resistant DSNU round cylinders, in several sizes and strokes, are used throughout the machine, according to Kevin Ost, Festo’s Kansas City area senior sales engineer. They have stainless-steel cylinder barrels and piston rods, and anodized aluminum bearings and end caps. Those handling small-to-medium loads feature Festo’s PPS internal cushioning, a self-adjusting end-position cushion that requires no adjustment. Units handling larger loads use adjustable end-position cushioning. Both types of cushions minimize impact and shock loads that could potentially damage the machine and cause premature cylinder wear.

In the large-box packing section, the FSPS-P makes similar use of rotary actuators and the corrosion-resistant DSNU cylinders with Viton seals (designed to withstand severe washdown environments) to sort and move the product. But here, chicken accumulates in center drawers that are alternately shuttled to packing stations on either side of the machine. This created an engineering challenge for Barnett because the FSPS-P is more than eight feet wide, and available space is constricted by conveyors running over and under the drawers’ travel paths. Here, he opted for Festo DGC rodless cylinders because of the long length, low profile, and structural support they offer.

The linear drives have a 1.2-m stroke with an 18-mm piston. The DGC’s sealing system consists of an outer cover strip and an internal sealing band that offers excellent contamination resistance with virtually no leakage, says Ost. Loads mount directly to the slides, which run on plain-bearing guides, and the units have adjustable end-of-stroke positioning and cushioning. Twenty of the DGC linear drives are used on the machine.

The valves are mounted in groups of eight throughout the machine in individual stainless-steel enclosures. “That puts the valves in close proximity to the actuators they are driving,” explains Barnett. “It gives us the benefit of not having lots of compressed air in long tubing lengths, which saves air and energy. Plus, we’re not introducing delays in the timing of movements — and timing is critical at the rates we’re talking about,” he emphasizes.

“It also gives us some modularity,” adds Barnett. Although this machine was custom built, the intent is to produce similar versions for other customers. “A large part of the variations in these types of machines is in the number of positions, which directly affects the number of actuators. So housing the valves in modules makes it easy and straightforward to scale the design to whatever the project demands,” he says.

Benefits of pneumatics

But why pneumatics, rather than electric drives? “Historically, pneumatics is used in this industry because it’s a proven solution,” says Barnett. “It needs to be as clean an environment as possible, and there are benefits just in the sanitation. Components are subject to extreme washdown conditions, high-pressure water spray and harsh chemicals, so we try to minimize the amount of electronics we put into that environment,” he says. And electromechanical belt drives offer the potential to generate and trap debris. Pneumatic cylinders handle the tough operating and washdown environment without harboring contaminants, explains Barnett.

It’s a must because durability is the most critical factor, as far as the customer is concerned, says company General Manager Oliver Hahn. “Reliability is so important. We don’t have the luxury to wait hours to get a machine up and running, should it fail. If it stops, the product can go bad rapidly.”

Clean, efficient, and reliable

The entire production process, even starting on the farm, is finely choreographed, adds Baader CEO Andy Miller. “Our customers raise birds for a specific number of days to meet a specific size range,” he explains. “If we have a delay, the birds grow larger, are the wrong size, and that throws off production, deliveries, and so on.” Or it spoils on the waiting truck or, if it’s already been processed, just sitting on an idle machine. “It’s critical in our industry to minimize downtime,” stresses Miller.

Another factor that can play havoc with equipment is that temperatures in food-processing plants vary widely, from extremely hot during washdown to extremely cold during production, explains Hahn. “So it’s not just the washdown we have to deal with; condensation is also inevitable. All these things play a big role when we design this type of equipment.”

Plus, the compressor might operate in a hot and humid environment, but compressed air is piped inside a cold room where meat is processed. Inevitably, this leads to condensation inside the air lines, says Miller. Making matters worse, many plants don’t have functional air dryers at the compressor. “The reality is that the air system is beyond our control, so we try to protect the machine as best we can and give the customer good advice on best practices,” he says. To that end, in addition to standard filtration on the incoming compressed air, they add a water separator and coalescing filter for extra protection.

Like most applications today, energy efficiency is also a concern, says Barnett. But that is balanced with the ability to run continuously under adverse conditions. For instance, the short tubing that runs from valves to cylinders, mentioned previously, reduces unnecessary compressed air consumption. Also, the company took advantage of Festo’s cylinder-sizing software to ensure the cylinders properly matched the application.

But energy savings is also a big issue on the hygiene side, explains CEO Miller. Washdown costs can be substantial, so the entire system must be designed for easy access to facilitate cleaning. For instance, mounting blocks of valves close to the actuators minimizes the number of hoses that must be routed along the length of the FSPS-P. And hoses are separated from one another, so each can be readily accessed and cleaned. Otherwise, keeping bundles of hoses clean in a food-processing environment poses a challenge.

“If you don’t do that, the number of people required for cleaning, and the amount of energy expended with high-pressure hoses, it is massive. So clearly, hygiene is a big part of energy savings, and we incorporate that into our design,” says Miller.

The FSPS-P was custom built for Baader’s sister company in Denmark for ultimate shipment to a customer in France, and that played a role in sourcing the pneumatics. Festo’s international reach definitely helped facilitate this project, says Hahn. “The service they provide makes our job so much easier. You can’t have delays on parts delivery. Because Festo is worldwide, if something goes wrong, that is a big benefit to us.”

But Baader has also built a reputation for equipment that is sophisticated yet simple, durable and effective. For that reason, they are meticulous in regards to manufacturing precision and sourcing high-quality parts. “We’ve had a good, long-term relationship with Festo,” adds Barnett. “They’re responsive to our needs, and a good source of ideas and suggestions when problem solving.”